Clinical significance of histologic subtyping of malignant pleural mesothelioma

Our plain-English summary of Clinical significance of histologic subtyping of malignant pleural mesothelioma, by L. Brcic, I. Kern (Translational Lung Cancer Research, 2020).

The study

• Authors: L. Brcic, I. Kern
• Journal: Translational Lung Cancer Research
• Published: 2020;9(3):924-933
• Type of article: Review
• Cited by: 68 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Malignant mesothelioma (MM) is uncommon, but very aggressive tumor arising from the mesothelial cells of pleura, pericardium, peritoneum, and tunica vaginalis. Despite multimodality treatments 5-year survival is only 5% after the diagnosis. Histology and TNM staging system are still the best prognostic factors. Furthermore, histologic subtype of MM determines the clinical management of the patients. According to the 2015 WHO classification, MM is divided into diffuse, localized and well differentiated papillary mesothelioma. Major histologic subtypes of diffuse MM, namely epithelioid, biphasic and sarcomatoid, have different prognosis. However, in the last decade it has become evident that more detailed subclassification and histologic/cytological characterization of MM have prognostic and perhaps predictive implications. In this review, major histologic subtypes and cytological features of MM are presented and their relation with prognosis and predictive biomarkers is discussed.

2020 Translational Lung Cancer Research. All rights reserved.

In plain English

This article was a narrative review, commissioned for a journal series on highlights of the 2019 Pulmonary Pathology Society meeting, by two authors from pathology institutes in Graz, Austria, and Golnik, Slovenia. It reported no new patient data. It summarized published studies on how the microscopic type of malignant mesothelioma relates to survival and treatment. The authors described rarer forms, well-differentiated papillary and localized mesothelioma, which have a better outlook than diffuse mesothelioma. They also described the three main diffuse types: epithelioid, biphasic and sarcomatoid. Cited studies reported that some epithelioid growth patterns were linked to better survival, while pleomorphic and transitional patterns had survival closer to sarcomatoid tumors. In one cited study of biphasic tumors, survival differed with the share of epithelioid tissue. The authors wrote that untreated patients with sarcomatoid mesothelioma die within 5 to 6 months. The review also discussed tumor markers such as PD-L1 and mesothelin. The authors concluded that the varied microscopic forms have prognostic significance and affect treatment decisions. They added that links between tumor appearance and predictive markers are still being developed. The review did not discuss asbestos.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Narrative review (commissioned review article); no new data collected
• Who was studied: No study population; the review covered published literature on the histology of malignant mesothelioma, mainly pleural, as part of a series on the 2019 Pulmonary Pathology Society Biennial Meeting
• Exposure: Not addressed; the review concerns tumor histologic subtypes and biomarkers and does not discuss asbestos or other exposures
• Main results:
  • Reviewed: localized malignant mesothelioma has a much better prognosis than diffuse mesothelioma and may be curable by complete surgical removal
  • Reviewed: in a study by Kadota et al., trabecular and tubulopapillary patterns were favorable prognostic patterns compared with other patterns in epithelioid mesothelioma
  • Reviewed: the transitional pattern is associated with survival similar to sarcomatoid and pleomorphic types
  • Reviewed: untreated patients with sarcomatoid mesothelioma die of the disease within 5 to 6 months
  • Reviewed: in a study by Vigneswaran et al. of biphasic mesothelioma, survival was 6.62 months for patients with less than 50% epithelioid component, 11.8 months for those with more than 50%, and 20.1 months for patients with pure epithelioid mesothelioma
  • Reviewed: histologic subtype assigned on small biopsy samples agreed with the diagnosis on surgical resection in 72 to 83% of cases
  • Reviewed: in a study of 214 samples from the MAPS trial, lower PD-L1 expression was linked to better overall survival, but this was no longer statistically significant after adjustment for histology and other factors
  • Reviewed: mesothelin, a target of new therapies, is not expressed in sarcomatoid mesothelioma
• The authors' conclusion: The authors concluded that the diversity in histologic presentations of malignant mesothelioma has prognostic significance and affects treatment decisions. They added that the correlation between morphology and predictive biomarkers is still being developed.
• Limitations the authors state:
  • The authors stated that diagnostic challenges, such as distinguishing reactive lesions, carcinomas and sarcomas, were outside the scope of the review
  • The authors noted that studies on the epithelioid share in biphasic mesothelioma are rare and use different cut-off values
  • The authors noted small numbers of patients and published studies for pleomorphic and transitional patterns

Topics

Medical terms in this study, explained in our Lexicon: Pleural Mesothelioma, Mesothelioma, Mesothelial Cells, Pleura, Pericardium, Peritoneum, Tunica Vaginalis, Histology.

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• Malignant peritoneal mesothelioma: prognostic significance of clinical and pathologic parameters and validation of a nuclear-grading system in a multi-institutional series of 225 cases — D.B. Chapel, J.J. Schulte, et al. (2021)
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• Clinical, histologic, and genetic features of mesothelioma in a 7-year-old child — A. Sugalski, M. Davis, et al. (2013)
• Diffuse Pleural Mesotheliomas with Genomic Near-Haploidization: A Newly Recognized Subset with Distinct Clinical, Histologic, and Molecular Features — S.R. Yang, G. Jayakumaran, et al. (2024)

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